1. Field of the Invention
The present invention relates to an imaging apparatus and an image blur correction method.
2. Description of the Related Art
An imaging apparatus has been known which corrects an image blur caused by the shake of the imaging apparatus due to, for example, a hand shake. The shake of the imaging apparatus includes an angular shake of the imaging apparatus about an axis perpendicular to an optical axis and a translational shake of the imaging apparatus in an axial direction perpendicular to the optical axis.
In the correction of an image blur caused by a rotational shake, in general, an angular velocity about the axis perpendicular to the optical axis is detected and the amount of rotational shake of the imaging apparatus is calculated. Then, a correction optical system or an imaging element is moved such that an image blur on an imaging surface of the imaging element is cancelled, on the basis of the amount of rotational shake.
In the correction of an image blur caused by the translational shake, acceleration in an axial direction perpendicular to the optical axis is detected and the amount of translational shake of the imaging apparatus is calculated. Then, the correction optical system or the imaging element is moved such that an image blur on the imaging surface of the imaging element is cancelled, on the basis of the amount of translational shake.
The influence of the translational shake varies depending on the object distance. In high magnification imaging at a short object distance, the influence of the translational shake increases. JP1995-225405A (JP-H07-225405) and JP1998-301157A (JP-H10-301157A) disclose an imaging apparatus that detects the position of a focus lens, acquires an object distance on the basis of the position of the focus lens, and corrects an image blur on the basis of the acquired object distance. In addition, JP2012-128356A discloses an imaging apparatus which calculates the amount of movement of the imaging apparatus in an optical axis direction from acceleration acting in the optical axis direction and corrects an object distance on the basis of the calculated amount of movement.
JP2005-173431A discloses an auto-focus device that comprises a so-called voice coil motor including a driving coil and a magnet. When a current is supplied to the driving coil, a driving force corresponding to the supplied current is generated by the voice coil motor and a focus lens is moved by the driving force of the voice coil motor.
Typically, feedback (closed loop) control that detects the position of a focus lens and aligns the detected position with a target focus position is used for focusing. In contrast, the auto-focus device disclosed in JP2005-173431A, the focus lens is biased in the optical axis direction by a holder spring and a current for generating a driving force matched with the biasing three of the holder spring at the focus position of the focus lens is supplied to the driving coil to move the focus lens to the focus position.
As such, in the auto-focus device disclosed in JP2005-173431A, open loop control in which the feedback of the position of the focus lens is omitted is performed for focusing and a position sensor is not required. Therefore, the size and weight of the auto-focus device are reduced.